We have developed an experimental mouse lymphoma system which may be used to test the age cohort variation hypothesis on the selection and monitoring of therapy at different times during tumor growth. Activities proposed for the coming period include: 1) Continuing investigation of the age cohort variation and chemotherapeutic sensitivity of C57BL ascitic lymphomatous tumors to a variety of chemotherapeutic agents. 2) Detailed investigation of the reappearance in chemo-sensitivity induced by therapeutic agents following tumor therapy. We are particularly interested in advanced tumor. Further study of radiation and the alkylating agents, nitrogen mustard, BCNU, cytoxan, which are cycle-non-specific chemotherapeutic agents, and show activities against actively proliferating or non-proliferating tumors may represent means of causing reproliferative activity. 3) We aim to perform radiobiological studies in the coming year on the Radiation sensitivities of varying age-cohort tumors. 4) Flow-micro Fluormetric studies of DNA per cell content during tumor growth following tumor therapy. 5) Preliminary experiments on DNA polymerase as a proliferation enzyme will be carried out as a function of growth stage and treatment for the ascites tumor. 6) We will develop a colony assay for the tumor.